|Portrayed by||David Lyons (adult)|
Patrick Johnson (teen)
|Also known as||Bass, Jimmy King (alias)|
|Residence||Jasper, Indiana (formerly)|
Philadelphia, Pennsylvania (formerly)
President of the Monroe Republic (formerly)
General of the Monroe Militia (formerly)
US Marine (formerly)
|Affiliation||Monroe Republic (formerly)|
United States Marine Corps (formerly)
|Family members||William Monroe (father) (deceased)|
Gail Ross Monroe (mother) (deceased)
Angela Lynne Monroe (sister) (deceased)
Cynthia Claire Monroe (sister) (deceased)
Connor Bennett - Son
|“||"Don't you walk away from me! You were the one who tried to kill me! You were the one that started all of this... and now you're walking away?"||”|
Before shipping out for basic training, Bass had a brief sexual relationship with Miles' then-girlfriend Emma Bennett. After Bass and Miles shipped out, she found out she was pregnant with his son. However, her parents refused to allow her to tell him and Bass had no knowledge of his son until many years later.
At some point, possibly during Operation Iraqi Freedom, Bass served two tours of duty in Iraq. In 2010, Monroe's family was killed when they were hit by a drunk driver on the way to a Harry Potter movie. As he was getting drunk and contemplating suicide in the cemetery, Miles arrived and talked him down.
By 2012, Monroe was a US Marine sergeant stationed at Parris Island, South Carolina along with Miles. Bass was in the car with Miles when the Blackout occurred, texting a woman named Susan. The Blackout disabled all the vehicles forcing the two Marines to walk to their base. Upon arriving, the security detail prompted the Marines to present I.D to enter, Monroe was lacking his identification, but noted an unidentified member of the security would vouch for him. Monroe then raised his arm, revealing a tattoo with a large "M" in a circle and "Monroe" beneath, which prompted the unidentified security member to allow him entry.
Eight weeks after The Blackout, Bass decides to accompany Miles Matheson when he announces that he is leaving the base and going to Chicago, as Miles is the only family that he has left. They took handguns from the base munitions depot and departed.
As they walked from Parris Island to Chicago, the two happened upon a young couple in an orange tent who had been murdered and their supplies taken. A little farther down the road, they encounter two men beating a third over his supplies. Bass initially says that they should keep going, but Miles confronts the pair. Monroe is shocked when Miles shoots the two men, but he helps Miles carry the beaten man to safety. Eventually, Bass, Miles, and Jeremy Baker formed the Monroe Republic in order to keep the region from falling into complete anarchy.
Eleven years after the Blackout, Miles felt that Monroe's lust for power was undermining his ability to govern the Republic and attempted to kill him, but was unable to pull the trigger. A drunken and depressed General Monroe summoned Tom Neville to his office in Philadelphia and tasked him with hunting down those responsible for helping Miles. Bass remarked how there was a part of him that wished Miles had pulled the trigger, and insists that Miles cannot be hunted down, as he is not an ordinary man but the creator of the Militia. Around this time, rumors began to circulate that Monroe had gone mad with power, even among Militia troops. He also began preliminary work on restoring electricity to the Republic at this time. Neville is brought before him to answer for snooping around in the basement. He then remarks how his work at getting the power back on is necessary to the survival of the Republic. Monroe then loads his pistol, disengages the safety, and offers Tom a drink. He then explains that the prisoner Tom saw was Miles' sister-in-law. To further their efforts at restoring power, he promotes Neville to captain and charges him with finding Ben Matheson, all the while encouraging Neville to be ruthless in his pursuit. During that time, Monroe has held Rachel Matheson hostage in hopes that she would help him in his endeavor to turn the power back on as Miles originally planned.
Fifteen years after the Blackout the Monroe Republic is led by Sebastian Monroe himself. Sebastian and formerly Miles Matherson had trained and led their soldiers to the point that their army was feared across the continent. Monroe sent soldiers to go and find Ben Matherson, as he knew something about turning the lights back on. So Monroe sent Tom Neville, a highly skilled Captain, and a company of troops. After months of searching they finally found him. There was a fight, in which Ben Matherson was killed. Later, at Kimberton Pennsylvania, Monroe himself is interrogating a captured Rebel, but kills him when he is unable to extract any information.
Bass is charismatic, charming with an all-or-nothing personality. He comes off as emotionally fragile when it comes to personal relationships. Although he was deeply devoted to Miles and viewed him as a brother, like many brothers do, Bass was sometimes jealous of what Miles had (sleeping with Emma and as he hinted, coveted Nora). After Bass's parents and sisters were killed by a drunk driver, Bass was going to commit suicide, but Miles talked him down. After the Black Out, Bass exhibited a strong loyalty to Miles, but he didn't care about the Republic or the men they were leading, which shows in his lack of interest in keeping the Militia in check. Bass is deeply paranoid after Miles tried to assassinate him. He carries his gun with him at all times after the attempt and once shot one of his advisors in the head after he heard about Neville's desertion and that his son, Jason, was not dead but alive and fighting with the Rebels. Bass comes off as a womanizer as well. With most of the women he has interacted with, he exhibits a charismatic, suave persona that is meant to put them at ease and easier to manipulate.
- Emma Bennett - Miles's ex-fiancé. She and Monroe had an affair which resulted in Monroe's son Connor. Monroe had no idea that he had a child until Emma told him, but before she could tell him where to find him, she was shot and killed.
- Connor Bennett - Monroe's son from his affair with Emma Bennett. It is revealed that even though Emma kept the child's existence a secret for many years, after witnessing how cruel Monroe became while leading the republic, she asked Miles to help her hide Connor from him. After finding out, Monroe demands that Miles tell him where his son is. They go together to Mexico, where they find him but Connor doesn't react well to the news of his father suddenly appearing. Choosing to be loyal to the cartel that took him in when he was starving on the streets, he sells out Monroe and helps capturing him. Later, he starts to doubt his decision and helps Rachel to rescue Monroe and Miles. His betreyal is found out and he escapes with Monroe. Their relationship remains strained but Monroe convinces Connor to help him restore the Monroe Republic.
- Rachel Matheson - She and Monroe used to be friends until Monroe decided to keep Rachel hostage after Miles abandoned the Militia. For years, Rachel refused to give up her secrets about the Black Out and how to turn the power back on, until Monroe kidnapped her son and brings him to Philadelphia as a hostage. Rachel attempted to kill Monroe (along with herself) by using a grenade. That planned failed. Once in the Tower, Rachel and Monroe were trapped in a bunker together and had a heart-to-heart where Rachel reveals that she blames him for Danny's death and Monroe reveals that he has a son and wants to make up for all the blood shed he's caused by helping Rachel save her daughter, Charlie. Rachel helps Monroe escape the bunker and Monroe saves Charlie's life.
- Nora Clayton - Miles's girlfriend. Monroe hints at the fact that he and Nora may have had a sexual relationship before she hooked up with Miles permanently. Monroe claims that he "was sometimes jealous of the things he had" leading on that he always wished he and Nora were together instead of her and Miles. Monroe had Nora tortured to the point of death in order to find out where Miles was hiding.
- Charlie Matheson - Miles's niece and Rachel's daughter. Monroe and Charlie have little interaction but when they do meet, Monroe seems always cordial and charming calling her by her full name, Charlotte. He saves Charlie's life in the Tower. When Charlie stood up and faced one of Monroe's soldiers when Rachel was being pressured to help Monroe build an amplifier, Monroe seemed impressed by Charlie's courage.
- Danny Matheson - Rachel's son and Miles's nephew. Monroe kidnaps Danny and has him brought to Philadelphia where he hopes he can pressure Rachel into helping him turn the power back on. It works so far until Rachel tries to build a bomb instead. Yet after Rachel kills Dr. Jaffe, Monroe resorts to more brutal methods to coerce Rachel's cooperation. Monroe reveals later that he is sorry for his indirect role in Danny's death.
- Tom Neville - Monroe's captain and until recently, his most loyal supporter. Monroe admired Neville's ability to seek the truth in any matter he set him to and so had him promoted to Captain. Monroe tasked Neville with finding and bringing Ben Matheson to Philadelphia, but Neville brought Danny instead after something went wrong, resulting in Ben's death. Monroe promotes Neville to Major and head of Intelligence and Interrogations to which Neville is grateful. However, their relationship soured when Monroe had Jason Neville, Tom Neville's son, tortured for information because he suspected him of being a spy. Neville suddenly realized that Monroe was becoming too paranoid and volatile. In fear, Neville and his wife ran from the Monroe Republic after Neville's failure to complete his mission and because Monroe would find out that Jason was alive and had joined the Rebels. In the Season Finale, Neville overthrew Monroe as General of the Militia and Monroe Republic.
- Despite the fact that he can manage a state with an iron-fist Monroe faces severe depression caused by his lack of friends and the fact that his family was killed in a car accident.